JPH0820225B2 - A device for measuring the diameter or width of thin wires - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION Conventionally, an apparatus for contactlessly measuring the diameter or width of a thin wire has been known in which a plane parallel beam having a width wider than the dimension of an object to be measured is used. Insert the object to be measured at a right angle to, and measure the width of the shadow generated by this with an image sensor, etc. in which photoelectric conversion elements are linearly arranged, or in a space where a thin laser beam scans at a constant speed, There is used a device in which an object to be measured is inserted at a right angle to a scanning surface of a laser beam and a wire diameter is measured from a time when the laser beam is shielded and a scanning speed. These devices are widely used in the field of product inspection because they can measure the dimensions of objects at high speed and in a non-contact manner.

[0002]

However, in these conventional devices, when the size of the object to be measured becomes several tens of micrometers or less, light is reflected behind the object to be measured due to the diffraction phenomenon at the edge of the object. Since it goes around, there is a problem that it is difficult to perform measurement with high accuracy. The present invention provides a method and an apparatus for measuring the dimension of a linear object or a band-shaped object whose thickness or width is several tens of microns or less with high accuracy by utilizing this diffraction phenomenon.

[0003]

The diameter or dimension measuring method of a linear object of the present invention which achieves the above object is to irradiate a linear object to be measured with a monochromatic parallel beam having a width larger than the width of the linear object. The scattered light is focused by the lens, f is the focal length of the lens, r is the distance from the focal point in the focal plane, and I (r /
When f) is the intensity of scattered light on the focal plane at r / f, obtain the diameter or width D of the linear object to be measured from the position where I (r / f) · (r / f) is maximum. Is characterized by.
Further, the theoretical value Ert of the energy of scattered light at the distance r
The diameter or width D can also be obtained by obtaining the value of D that minimizes the sum Σ (Erm−Ert) ² of the error between the measured value Erm and the measured value Erm.

[0004]

The principle of measurement will be briefly described with reference to FIG.
A linear object 2 having a diameter or width D is irradiated with a monochromatic parallel beam 2 having a width d larger than the width D, and scattered light 3 is collected by a lens 4. The intensity distribution I of the scattered light on the focal plane 5 of this lens is I (r / f) = D ² sin ² {(πD / λ) (r / f)} / {(πD / λ) (r / f) ² }, as shown by the solid line in FIG. λ is the wavelength of the monochromatic light emitted, f is the focal length of the lens, and r is the distance from the focal point on the focal plane. R to this intensity distribution
According to theoretical calculation, I (r / f)  (r / f) obtained by multiplying / f is r / f = 1.
It becomes a maximum at 165 / (πD / λ). The position of this maximum is uniquely determined by the size of D. By utilizing this, the distance r at which the scattering intensity is maximum can be obtained from the scattering intensity signal obtained by the array in which the photoelectric conversion elements are arranged, and the dimension D can be determined from this. Alternatively, the energy of scattered light received by the i-th element of the array is set to Ei, and the theoretical value Eit and the measured value Eim are best matched, for example, the sum of squared errors Σ (Eim−Eit) ²
The wire diameter D can be determined by repeatedly obtaining the value of D that minimizes

[0005]

EXAMPLE FIG. 2 shows an example of the apparatus for measuring the diameter or dimension of a linear object according to the present invention. A parallel laser beam 11 irradiates a fine line (object to be measured) 12, and scattered light 13 by the fine line is focused on a focus O by a light receiving lens 14. The partial annular photoelectric conversion element 18 is provided on the focal plane of this lens.
Array 19 of is placed. The current of each element 18 is converted into a voltage signal by the signal processor 15, the size of the wire diameter is calculated by the above-mentioned method in the calculator of 16 and displayed on the display unit 17. The sensor 18 for detecting the intensity of scattered light may be a linear array, but in this case, it is necessary to hold the measured object so that it is perpendicular to the direction of the array of elements.
If the sensor in which the ring-shaped photoelectric conversion elements 19 are arranged as shown in the figure is used, it is not necessary to keep the measured object 12 in a specific direction. This ring-shaped photoelectric conversion element does not need to cover 360 ° with respect to the focal point O, and θ is practically used.
Any partial annular photoelectric conversion element that covers about 45 ° may be used.

[0006]

FIG. 3 shows an example of measurement by the method and apparatus of the present invention. (A) is 18 μm, (b) is 25 μm,
(C) is a measurement example of a thin line of 30 μm, and the dotted line showing the theoretical value and the solid line showing the measured value are in good agreement, and the wire diameter can be easily obtained. INDUSTRIAL APPLICABILITY As described above, the present invention positively utilizes the diffraction phenomenon which has been a cause of lowering the measurement accuracy in the conventional measurement method, and uses a simple device to form a linear or strip-like shape of several tens of microns or less, which has been difficult in the past. I was able to measure the width of my body accurately.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a measurement principle for measuring the diameter or width of a thin wire of the present invention.

FIG. 2 is a conceptual diagram showing the configuration of one embodiment of an apparatus for measuring the diameter or width of a thin wire of the present invention.

FIG. 3 is a graph showing measured values by the apparatus of the above-mentioned embodiment.

[Explanation of symbols]

1, 12 thin line to be measured 2, 11 laser beam 3, 13 scattered light 4, 14 lens 5 focal plane 15 signal processor 16 calculator 17 display 18 photoelectric conversion element 19 sensor array

Claims (4)

[Claims] 1. A linear object to be measured is irradiated with a monochromatic parallel beam having a width larger than its width, the scattered light is focused by a lens, f is the focal length of the lens, and r is the focal point from the focal plane. When the distance and I (r / f) are the intensity of scattered light on the focal plane at r / f, the diameter of the linear object to be measured is measured from the position where I (r / f) · (r / f) is maximum. Alternatively, a method for measuring the diameter or width of a thin line characterized by obtaining the width D 2. A linear object to be measured is irradiated with a monochromatic parallel beam having a width larger than its width, the scattered light is focused by a lens, f is the focal length of the lens, r is the focal point from the focal plane. When the distance is defined as a distance, the value of D that minimizes the sum Σ (Erm−Ert) ² of the error between the theoretical value Ert of the scattered light energy and the measured value Erm at the distance r is characterized. How to measure the diameter or width of thin wires 3. A monochromatic light source, a linear object to be measured illuminated by a parallel beam from the light source, a lens for receiving light scattered from the linear object, and a focal point of the optical lens. consists of a photoelectric conversion element array, means for sensing current signals from these elements, the display for displaying the device and wire diameter for analyzing the resulting intensity distribution, the analysis
The device is f the focal length of the lens, r the focal point in the focal plane
Distance from, I (r / f) on the focal plane at r / f
When the intensity of scattered light is I (r / f) · (r / f),
Arithmetic circuit to be obtained and obtained I (r / f) · (r / f)
It includes an arithmetic circuit that calculates r / f that maximizes
Apparatus for measuring the diameter or width of the linear object to symptoms 4. The linear object diameter or size measuring device according to claim 3, wherein the photoelectric conversion element array is a partial annular photoelectric conversion element.